There are two basic problems that arise when optical fibers are used in Local Area Networks (LAN's): (a) what type of "wiring" scheme is to be used to connect the LAN's plurality of computers (stations) so that each station may communicate with another and (b) what type of interconnection techniques and facilities are to be employed so that stations may be added and removed as required of the LAN matures and changes from time to time. Applicants have found that one way to solve these problems is by means of the disclosed novel fiber optic wiring center that can accommodate and adapt to a bus, ring and point-to-point type fiber optic circuit as well as being able to interconnect with addtional and/or delete stations as the demand arises from time to time.
Local Area Network technology, as it presently exists, raises two concerns in the mind of a potential user: the first is the debate or uncertainty about the selection of the optimum LAN architecture/protocol, and the second is the anticipated obsolescence of existing networks. A potential user may be reluctant to install a fiber optic LAN network because the technology of fiber optics is moving so fast and corresponding obsolescense is ever present. For example, future technology may require a network with a different topology and protocol and may require rewiring a building or campus, resulting in high cost to the user. It is towards the solution of these two concerns of Local Area Networks--the reconfigurability from a Carrier Sensitive Multiple Access Collission Detection (CSMA/CD) bus network to a ring network on to a point-to-point network--that this invention is directed.
In case of LAN's problems of obsolescence and migration to different topologies are easier to solve if optical fibers are used as transmission medium. Local Area Networks are of these major types, multiple access bus such as CSMA/CD, ring types and point-to-point. Each of these types can take on the same star shaped topology when fiber optics are used as a transmission medium. Prior art multi-access bus type fiber optic networks use a star coupler to emulate a passive bus in which the central node consists of a star coupler connected to optical fibers drawn from nodes or stations located throughout a given building or campus.
For ring type networks, a star shaped topology is preferred for various reasons, including the convenience of implementation and maintainability. In this case, the central node consists of an array of interconnections allowing the fibers to be serially connected to form a ring. One type of a LAN is referred to as an Ethernet type system. It has a bus type configuration only. Another type of LAN, a token ring, usually has a ring type topology. Still another is a point-to-point system. All may be defind as a plurality of computers or stations connected together so that one computer or station may communicate with another. The problem then reduces itself down to the requirement or need of a fiber optic interconnection scheme and apparatus that will permit efficient transition back and forth from one type of network (ring) to another (bus).
Local Area Network interconnection system has a different set of priorities and problems than the priorities and problems of long haul trunk telecommunication networks. LAN's typically have a geographic coverage of only a few kilometers, but they require a large number of interconnections to provide access to the LAN by the various stations. Consequently, splicing speed and accessibility is quite important and ultra low splice loss is not all that critical as it is in long haul trunk type telecommunication networks. Furthermore, an installed LAN can be expected, if not guaranteed, to undergo reconfiguration during its life time; consequently, a re-enterable splice is therefore an option that is not only desirable but almost a requirement.